This is a thesis of two halves.
In the first half of the thesis, the construction of C–C bonds from carbon monoxide units is developed using a mixed transition-metal and main-group metal strategy. In chapter 1, synthetic methods for CO homologation were reviewed. In chapter 2, the formation of carbon–carbon bonds using carbon monoxide as a feedstock was investigated. Reaction of an aluminium(I) reagent with a transition-metal carbonyl resulted in the formation of C–C bonds between CO monomers to form isolable C2, C3, and C4 species. The mechanism was explored using density functional theory calculations and isotope labelling experiments. Control of the chain topology is demonstrated through variation of the transition metal fragment. CO units within the final carbon chain originate from both gaseous CO and transition-metal bound CO units. In chapter 3, the insertion of CO into Al–C bonds was further studied through the reaction of strained aluminacycles with CO gas. The reaction was found to be reversible and was studied using a combination of kinetics and density functional theory calculations. The insertion of CO into Al–C bonds was calculated to proceed via an asynchronous but concerted transition state. The synthetic and theoretical work in chapter 2 and 3 are linked through fundamental reactions involving migratory insertion at either transition metal or main group centres.
In the second half of the thesis, the deconstruction of C–C bonds was explored using main-group metals. In chapter 4, the cleavage of C–C bonds in alkylidene cyclopropanes using either an aluminium(I) reagent or magnesium(I) reagent was investigated. The reaction was studied using a combination of density functional theory calculations and kinetics. The reaction of a carbon–carbon double bond in the substrate with the main-group reagent preceded C–C cleavage. The mechanistic insights were used to develop magnesium-based catalysis for C–C bond hydrosilylation. In chapter 5, the reaction of an aluminium(I) reagent with biphenylene was studied. The activation and cleavage of the arene ring was achieved, forming two isomeric products. The integrity of the strained 4-membered ring was observed throughout the course of the reaction. The reaction was studied using density functional theory calculations and a full calculated pathway from the reagents to the products was discovered. The activation strain model was applied to understand the chemoselectivity of the reaction and showed that the position and extension of the frontier molecular orbitals of the aluminium(I) reagent underpin its unique reactivity.